This invention relates generally to single component developers, and more specifically to single component conductive toners containing magnetic materials, which toners are useful for example in the production of high quality images in electrophotographic systems, and in various other imaging systems including commercial printing machines, such as Versatec printers. The toner compositions of the present invention are unique in that for example lowenergy outputs can be employed for causing the fusing of said compositions to a substrate, which fusing can be accomplished subsequent to the application of the toner composition to the image, and transfer of the development image to a substrate, such as paper.
The production and development of images, particularly xerographic latent images is well known and is described in many prior art publications and patents. In one development sequence, there is employed developer materials such as toner, which when blended with a suitable carrier is referred to as the developer composition. Subsequent to development, the latent image can be transferred from the photoconductive surface, such as selenium, to a suitable substrate such as paper and thereafter fixed or fused to the paper substrate. Various fixing methods can be employed including vapor fixing, heat fixing, pressure fixing or combinations thereof, as described for example in U.S. 3,539,161. Many methods are known for applying the toner to the latent photoreceptor image including cascade development, magnetic brush development, powder cloud development and the like. In the magnetic brush system, magnetically manageable carrier particles are employed. In this system a magnetic force is used to provide adherence of the developer (carrier and toner) to a support member, which is then presented to the image bearing member. Magnetic brush development fills in solid areas, in very well compacted and does not depend on gravity to present the toner to the latent image bearing surface, as is necessary with free flowing cascade development, a factor which allows freedom in locating the developer station.
There are also known systems for magnetic development wherein the carrier material is not utilized, one such system being described in U.S. Pat. No. 2,846,333. This patent teaches the use of a magnetic brush to apply toner particles formed of ferrites and resin material to develop electrostatic latent images. One difficulty encountered with the process is that the conductivity of the toner renders electrostatic transfer rather difficult. However, such processes have been used commercially when special papers are employed, such as coated papers like zinc oxide paper.
A further development system using magnetic development is illustrated in U.S. Pat. No. 3,909,258 wherein an electrostatic development process utilizing a magnetic brush without carrier is illustrated. A toner suitable for use in this process is disclosed in U.S. Pat. No. 3,639,245, (Nelson) wherein a dry toner powder having specific electric conductivity is disclosed. The toner of this patent is formed by blending magnetite with a resin, and subsequently pulverizing the resulting material to a small particle size. The resulting particles are then mixed with carbon black, and small particle size silicon dioxide particles to improve flowability.
In another form of development of electrostatic charge patterns, there is employed a conductive one component toner which is contained on a conductive support member, and is brought into contact with the charge pattern bearing member as described in U.S. Pat. No. 3,166,432. In this situation the toner particles are held to the support member by Vanderwaals forces, and the conductive support member is held at a bias potential during development. This technique is particularly adaptable to solid area coverage and further requires only one component in the development material.
There is also known a method of developing electrostatic charge patterns employing an electroscopic toner particles suspended in a liquid system. With the proper choice of material, the toner, which is dispersed in a liquid, the toner becomes charged to a definite polarity. When the electrostatic charge pattern bearing member is brought into contact with the liquid suspension, the toner particles deposit where there is a preponderence of charge of the opposite polarity, as is the situation in cascade development.
Systems are also known where liquid developer materials are used instead of dry materials for the purpose of developing images, such as latent electrostatic images, and images or data and graphs produced by commercial printers and recorders. Liquid developer materials main disadvantage is that a solvent must be employed as part of the developer mixture, which solvent evaporates and causes undesirable odors, and possibly potential toxicity problems. In electrography, liquid ink techniques are utilized to develop electrostatic images produced by air ionization from writing nibs on dielectric coated paper.
There is thus a continuing need for toners suitable for use in one component conductive magnetic development systems and in particular toners which can be fused at relatively low fusing temperatures, referred to in the art as low melt toners, and which toners have adequate flow properties to render them highly useful for developing images in electrophotographic and printing machine systems.